Great question, Sarah! When you're sick, especially with a fever, your BBT readings won't be reliable for fertility tracking. The best practice is to mark these temperatures as 'disturbed' on your chart (most apps have a way to do this). You'll need to rely more heavily on your other fertility signs during this time, particularly cervical fluid observations. If you're seeing fertile-quality cervical fluid, it's best to consider yourself potentially fertile until you can confirm ovulation with a clear temperature shift after you've recovered. Don't worry too much about one cycle being a bit harder to interpret - it happens to all of us! The more cycles you chart, the more confident you'll become in recognizing your patterns, even with occasional disruptions.

I had the same issue last winter! What helped me was marking the temps as 'disturbed' like Emma suggested, but still recording them. Then after I recovered, I could see when my temperature returned to my normal pattern. One thing I noticed was that even though the actual temperatures were higher during my illness, I could still see a relative shift after ovulation. It wasn't as clear as usual, but looking back, the pattern was still somewhat visible. Definitely focus on your cervical fluid during this time - it's your most reliable sign when temperatures are affected by illness.